My Impressions of Pentax Fit Lenses

I have a collection of what could be termed middle ranking Pentax fit lenses, barring one, they are all intended for manual focus, and I don't have any really expensive exotic glass.

Over the years I have tried to carry out formal tests using both film and, using a Pentax to Canon adapter, my Canon 20D DSLR. I have come to the conclusion that, despite being very careful and methodical in my testing procedure, it is very difficult for an amateur to get meaningful results from such tests. Sure you can spot a real "dog" with an off centre element or other obvious malady and you really should test a new lens thoroughly in case it has to be returned, but it is really difficult to discriminate between good lenses in this way. A much better method, I have found, is to use them to take real photos. Over a period of time you get to know the glass that can make a scene really "pop", even in poor light, and those that are fine in bright contrasty conditions but cannot deliver the goods when the chips are down.

Most of my lenses were bought second-hand, and age and rough usage do not improve glassware. It is possible that my particular copy of any given optic is sub standard, so don't get too upset if I badmouth your favourite optic.

First a brief note about the history of Pentax glassware.

In the beginning there were the M42 screw threaded lenses, and you can fit them to your K bayonet camera with an appropriate adapter. Get a Pentax adapter as they are cheap second hand and very accurately made. It is not possible to use the auto stop down feature of an M42 lens on a bayonet mount. You therefore have to focus at full aperture and then stop down to the required aperture to take the shot - not incredibly convenient. There are many fine M42 lenses available however with a variety of companies making them, including people such as Zeiss.

The Pentax bayonet system was christened K, so we have K fit lenses. The first batch had no other appellation, they are just  known as K lenses.

Following the K series came the M optics to match the wonderful ME and MX cameras. The M series bodies were made smaller and the lenses were also trimmed down to suit. Advances in lens design mean that in many instances there came an improvement in performance, but that is not always the case, and some of the older K lenses are optically superior, if bigger and heavier.

The next lot offered electrical coupling to the camera for the purposes of setting the aperture from the camera body, and they were known as the A series, presumably because they were "Automatic". Users of Pentax digital cameras will pay a premium for these lenses, so their price is disproportionally high. You can use an A series lens on a non auto fitted body by switching the auto aperture feature off.

Following on from the A series came batches of cheap auto focus consumer zooms and mega expensive wonder glass, neither of which I normally deal with. Until, that is, Samsung took up the K mount and worked with Pentax to produce a digital camera. They, I assume, then re-badged some Pentax lenses and offered them under the Samsung name. When they withdrew the 35mm f2 from sale I managed to buy one new for a fraction of the original price and it is a very good lens indeed.

My favourite glass is as follows: -

28mm K f3.5 - better in my view than the M variants of which I have two. I use the K lens despite the fact that it has a none standard (for Pentax) filter size.

Pentax 28mm lenses

Three 28mm lenses,  f2.8 M,  f3.5 K  and  f3.5 M

35mm Samsung D-Xenogon f2 (clone of Pentax auto focus lens) and K f3.5, both excellent, but the Samsung is lighter and the wider aperture allows easier focusing. The only drawback is that the lens was designed for auto focus and the focus ring is a good deal slacker than on a manual focus lens.



35mm f3.5 K and Samsung 35mm D-Xenogon

50mm f1.7 M.  - I also have the 50mm f1.4 in both K mount and M42, but I cannot detect any useful improvement in optical quality in using that bigger and heavier lens. Quality is variable however, I have 3 copies of the f1.7 and they are all produce slightly different results! I also have the f2 variant, but have not used it sufficiently to come to any conclusion about its performance.

Pentax 50mm lenses

Three 50mm M lenses, the f2,  f1.7  and  f1.4

The 75-150mm M f4 zoom is a bargain, sharp and contrasty and able to hold its own against the 135mm fixed focal length variants. It's a much more useful lens in my opinion, but sells for less.

Pentax Telephotos

135mm f3.5 M,  75-150mm  f4 M,  200mm f4 M

OK without being stellar

28mm f2.8 M

28mm f3.5 M

135mm f3.5 M

135mm f2.5 Takumar in K fit - surprisingly good for a cheapo lens

200mm f4 M

Tamron Adaptall 2 200mm f3.5. Possibly a tad sharper than the Pentax but my copy is more prone to chromatic aberration (CA).

To be used only in emergencies

Tamron Adaptall 2 f2.5 24mm - razor sharp in the centre but rapid and marked fall off across the image. Lacks contrast. My only Pentax fitting 24mm lens, the Pentax equivalents go for silly money.

Tamron SP f8 500mm mirror lens -  This is my only experience with a mirror lens, and I am told that the Tamron SP is one of the best 3rd party 500mm mirror lenses about, but it has the characteristics of all mirror lenses, with poor contrast, less than wonderful sharpness, and those horrible out of focus rings. I could not afford to buy a conventional 500mm lens however so this one remains in my collection.

Almost there, but not finding a place in my camera bag

Pentax A f4 35-70mm zoom - having discovered the 75-150 f4 I wanted a similarly good zoom lens that would cover the shorter focal length range. Sadly the 35-70mm  is in my view just not quite good enough to replace the primes in this range.

Tamron Adaptall 2 f3.5-4.5 35-70mm zoom - rescued from a trip to the skip at work! Similar performance to the Pentax lens.

Zeiss Flektogon 35mm f2.4 - this is an excellent M42 lens, not quite as sharp as my two favourite 35mm lenses at f3.5, but possibly slightly sharper than the f3.5 K 35mm when stopped down. I would have no hesitation about using it in terms of its optical quality, but the build is not brilliant ( I have had one fail during a cycle tour) and there is no reason to put up with the lack of auto stop down as I have equivalent lenses in K fit that don't have that problem.

To be avoided

Pentax A f3.5-4.5 28-80mm zoom - execrable image quality and build! I have encountered two specimens and they both had incredibly slack and wobbly focusing rings.

Bryan Attewell
22-09-2008